Glucose-monitoring methods and devices involve a variety of physico-chemical transduction principles including optical, amperometric to viscometric techniques. Currently, the most common method of blood glucose sensing is based on an electro-enzymatic sensing. This approach requires blood to be drawn and tested and often requires a finger stick to draw blood each time a reading is needed. This methodology is often time-consuming and can be painful. Minimally invasive approaches based on needle-type sensors (e.g. glucose-oxidase) have been investigated. While these approaches are less painful, the measurement of glucose in interstitial fluid has well-known limitations (oxygen dependence, diffusion-controlled). For example, since signal formation in enzyme sensors depends on the rate of glucose consumption, any process that may affect mass transport of glucose from tissue to sensor (e.g. by protein and cell depositions on membrane, or by fibrotic capsule formation) compromises the accuracy and stability of the glucose measurement.
Temperature-stable devices for glucose sensing are important to treatments and control of diabetes. Diabetes is a chronic disease characterized by a disorder of the metabolism of insulin, carbohydrate, fat, and protein, as well as in the structure and function of blood vessels. Diabetes is currently the leading cause of death in the USA and other countries. Estimates indicate that diabetes has reached epidemic proportions worldwide, with between 5 and 10% of the world population affected. Diabetes is expected to become the primary disease worldwide in the future. Intensive management of blood sugars through frequent monitoring is effective to prevent, or at least manage, the progression of diabetic complications such as kidney failure, heart disease, gangrene, and blindness. Maintaining blood glucose levels near normal levels is typically achieved by frequently monitoring blood glucose levels.
Accurate quantitative blood sugar analysis depends, in part, on the monitoring conditions such as sugar composition, buffer strength and pH. Temperatures ranging from 30° C. to 45° C. are also a common feature of many sugar-monitoring applications. At these temperatures, however, many biomolecules, such as proteins, become extremely unstable and prone to denaturation within a short period of time. Any technology involving sugar-specific receptor molecules which is intended to be used for monitoring sugar levels over long periods of time such as several days, weeks or even months, needs to generate a stable output, ensuring good reproducibility and minimal re-calibration requirement. Long-term continuous glucose monitoring in bioreactors or in patients with diabetes mellitus necessitates a heat-stable output, since the temperature is around 37° C. There is a need for new methodologies and devices which provide functional stability during continuous sugar detection at elevated temperatures over a long period of time.